Urogenital System

The
excretory and reprodutive systems of vertebrates are closely integrated and
are usually studied together as the urogenital system. However, they do have
different functions: the excretory system removes wastes and the reproductive
system produces gametes (sperm & eggs) and provides
an environment for the developing embryo.

Excretory Organs

1. The primary organs of
the excretory system are the kidneys. Locate these large bean shaped
structures located toward the back of the abdominal cavity on either side of
the spine. Renal arteries and veins supply the kidneys with blood.

2. Locate the delicate ureters
that attach to the kidney and lead to the bladder. Wiggle the kidneys to help
locate these tiny tubes.

3. Procedure:
Remove a single kidney (without damaging the other organs) and dissect it by
cutting it longitudinally. Locate the cortex (the outer area) and the
medulla (the inner area).

4. The urethra carries
urine from the bladder to the urethral orifice (this orifice is found
in different areas depending on whether you have a male or female rat).

5. The small yellowish glands
embedded in the fat atop the kidneys are the adrenal glands.

**You are responsible for knowing the structures of both sexes. Locate the structures in your own rat and then observe the structures of the opposite sex from another group's rat.

The Reproductive Organs of the Male
Rat

1. The major reproductive
organs of the male rat are the testes (singular: testis) which are located
in the scrotal sac. Cut through the sac carefully to reveal the testis.
On the surface of the testis is a coiled tube called the epididymus,
which collects and stores sperm cells. The tubular vas deferens moves
sperm from the epididymus to the urethra, which carries sperm though
the penis and out the body.

2. The lumpy brown glands
located to the left and right of the urinary bladder are the seminal vesicles.
The gland below the bladder is the prostate gland and it is partially
wrapped around the penis. The seminal vesicles and the prostate gland secrete
materials that form the seminal fluid (semen).

The Reproductive Organs of the Female Rat

1. The short gray tube lying
dorsal to the urinary bladder is the vagina. The vagina divides into
two uterine horns that extend toward the kidneys. This duplex uterus
is common in some animals and will accomodate multiple embryos (a litter). In
contrast, a simple uterus, like the kind found in humans has a single chamber
for the development of a single embryo.

2. At the tips of the uterine
horns are small lumpy glands called ovaries, which are connected to the
uterine horns via oviducts. Oviducts are extremely tiny and may be difficult
to find without a dissecting scope. Procedure:
Pin the organs of the urogenital system.